1. Field of the Invention
The present invention relates to a fixing device that executes phase control for AC power on heaters, an image forming apparatus including the fixing device, and a heating control method executed by the fixing device.
2. Description of the Related Art
In recent years, image forming apparatuses employing an electrophotographic process such as a copying machine, a printer, a facsimile, and a multi-function peripheral configured by combining these apparatuses include a scanner unit for scanning an image, an engine unit for forming a toner image corresponding to an image scanned by the scanner unit on transfer paper, and a fixing device for fixing the toner image on the transfer paper formed by the engine unit using a fixing roller and a pressure roller.
The fixing device causes heaters to generate heat with an AC voltage supplied from an AC power supply and heats the fixing roller using the heaters caused to generate heat. To keep the temperature of the fixing roller heated to specific temperature in a fixed range, the heaters repeat to be turned on and off at a fixed time interval.
In causing the heaters to generate heat with a supplied voltage, to control occurrence of a flicker and occurrence of a harmonic current, for example, Japanese Patent Application Laid-open No. 2005-176485 discloses a technology for executing phase control for an AC voltage.
However, in the technology in the past, ON widths in respective half-wave periods of the AC power subjected to the phase control are stored in a memory, the respective ON widths stored in the memory are read out, and the heaters are caused to generate heat based on the read-out respective ON widths. Therefore, an extremely large capacity of the memory for storing the ON widths is required.